\\ T^alfa in SV, 40/4.
\\ alfa has to be a partition of [1,...,n]. Sum of
\\ t_svmatrixsel(T,A)/|A| for A in alfa.
t_svmatrixpart (T,alfa) = {my (n=matsize(T)[1],S);
S=t_zeromatrix(n); for (i=1,#alfa,A=alfa[i];
D=t_svdeltamatrix(n,A); S=S+D*T*D/#A); S}

\\ T^A in SV, 33/2. Obtained from T setting to 0
\\ the (i,j)-th element if i and j do not both belong to set A.
t_svmatrixsel (T,A) = {my (n=matsize(T)[1]);
matrix(n,n,i,j,if(setsearch(A,i)&&setsearch(A,j),T[i,j],0))}

\\ x^A in SV, 33/2. Obtained from x setting to 0
\\ the i-th element if i does not belong to set A.
t_svvectorsel (x,A) = vector(n,i,if(setsearch(A,i),x[i],0))

\\ x_A in SV, 35/3. [x[i1],...,x[is]] for A={i1,...,is}
\\ with i1<i2<...<is.
t_svvectorchoice (x,A) = {my (s);
s=select(i->setsearch(A,i),[1..#x]); apply(i->x[i],s)}

\\ Obtained from identity matrix setting to 0 all i-th
\\ diagonal elements for which i does not belong to set A.
t_svdeltamatrix (n,A=0) = if(!A,matid(n),\
matrix(n,n,i,j,if(i==j&&setsearch(A,i),1,0)))

t_svonesmatrixpart (n,alfa) = t_svmatrixpart(t_onesmatrix(n),alfa)

t_svonesmatrixsel (n,A) = t_svmatrixsel(t_svonesmatrix(n),A)

t_svonesvectorsel (n,A) = t_svvectorsel(t_svonesvector(n),A)